Page:UK Traffic Signs Manual - Chapter 5 Road Markings. 2003 (Sixth Impression 2009).pdf/68

10GRADE SEPARATED JUNCTIONS

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DESIGN

10.1 Grade separated junctions may involve merging and diverging lanes, or the gain or loss of lanes, or a combination of these. As junctions become more complex, so road marking layouts become more complicated. It is not practicable to detail all possibilities, but the standard principles should be followed. Reference should be made to TD 22 / 92 in Volume 6 of the Design Manual for Roads and Bridges (see para 1.4) for further guidance. When designing a complex layout, it should be borne in mind that it must be capable of being signed and marked in a way that drivers can readily understand.

MERGING AND DIVERGING SLIP ROADS

10.2 The layout of markings and road studs at the simplest grade separated junction is shown in figure 10-1. The principal dimensions are detailed in tables 10-1 and 10-2. This arrangement is suitable forone or two-lane exit and one-lane entry slip roads.

10.3 The nosing of the slip road is marked using diagram 1042 (varied where appropriate to reverse the direction of the chevrons, see para 4.62). Red studs are provided at 3 m centres along the outside of both edges.

Table 10-1 Merge and lane-gain markings

Road type	Speed limit (mph)	Length of entry taper (m)	Taper for minimumangle at nose	Nose length (m)	Length of ghost island tail (m)	Width of diag 1010 marking (mm)
		(1)	(2)	(3)	(4)
Rural motorway	70	205	1 in 40	115	180	200
Rural dual carriageway	70	150	1 in 30	85	150	200
	60 or less	130	1 in 25	75	150	150
Urban road	60	95	1 in 15	50	n/a	150
	50 or less	75	1 in 12	40	n/a	150

NOTE: Numbers (1) to (4) at the head of the above columns relate to features shown on figures 10-1 to 10-6.

Table 10-2 Diverge and lane-drop markings

Road type	Speed Limit (mph)	Length of exit taper(m)		Taper for minimum angle at nose	Nose length(m)	Width of diag 1010 marking (mm)
		1 lane	2 lanes
		(5)1	(6)1,2	(7)2	(8)2
Rural motorway	70	170	185 (150)	1 in 15	80	200
Rural dual carriageway	70	150	150 (120)	1 in 15	70	200
	60	130	130 (110)	1 in 15	70	150
Urban road	60	95	110 (90)	1 in 15	50	150
	50 or less	75	90 (75)	1 in 12	40	150

NOTES

1. Taper lengths refer to 2×3.65 m lanes, or, in brackets, 2×3.00m lanes.
2. Numbers (5) to (8) at the head of the above columns relate to features shown on figures 10-1 and 10-7.

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